Display device

ABSTRACT

A display device includes a substrate; a first electrode and a second electrode arranged to be spaced apart from each other on the substrate; a first insulating layer on the substrate; a light emitting element on the first insulating layer, located between the first electrode and the second electrode, and including a first end portion and a second end portion; a third electrode on the substrate and electrically connected to the first electrode and the first end portion; a fourth electrode on the substrate and electrically connected to the second electrode and the second end portion; a second insulating layer on the substrate and covering the light emitting element, the third electrode, and the fourth electrode; and a light diffusion layer on the second insulating layer and including a light diffusion particle.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2019-0073076, filed on Jun. 19, 2019 in the KoreanIntellectual Property Office, the entire content of which isincorporated herein by reference.

BACKGROUND 1. Field

Aspects of embodiments of the present invention relate to a displaydevice.

2. Description of the Related Art

A display device may display an image by using a light emitting element,such as a light emitting diode, as a light source of a pixel. The lightemitting diode exhibits relatively good durability under harshenvironmental conditions and exhibits excellent performance in terms oflifetime and luminance.

Recently, a research is underway to manufacture a light emitting diodeby using materials of highly reliable inorganic crystal structure and touse it as a light source of a pixel of a next generation by disposing iton a panel of a display device. As a part of this research, developmentof a display device for manufacturing a light emitting diode with asmall scale, such as a microscale or nanoscale, and for using it as alight source of each pixel is underway.

SUMMARY

According to an aspect of embodiments of the present invention, adisplay device includes a light emitting element. According to anotheraspect of embodiments of the present invention, light emitting elementsmay be arranged in a display device with a certain (e.g., predetermined)position and distance.

At this time, light emitted from the light emitting element, which is apoint light source, may be visually recognized in a certain (e.g.,predetermined) pattern to a user. When adding a separate light diffusionmember on a display device, optical characteristics of a display devicesuch as luminance may be deteriorated.

According to an aspect of embodiments of the present invention, adisplay device with improved uniformity of light emitted withoutdeteriorated optical characteristics is provided.

However, aspects of embodiments of the present invention are not limitedto the aspect mentioned above, and other aspects and technical objectsthat are not mentioned may be clearly understood by a person of anordinary skill in the art using the following description.

A display device according to one or more embodiments of the presentinvention includes: a substrate; a first electrode and a secondelectrode arranged to be spaced apart from each other on the substrate;a first insulating layer on the substrate; a light emitting element onthe first insulating layer, located between the first electrode and thesecond electrode, and including a first end portion and a second endportion; a third electrode on the substrate and electrically connectedto the first electrode and the first end portion; a fourth electrode onthe substrate and electrically connected to the second electrode and thesecond end portion; a second insulating layer on the substrate andcovering the light emitting element, the third electrode, and the fourthelectrode; and a light diffusion layer on the second insulating layerand including a light diffusion particle.

The light diffusion particle may include at least one of a silvernanowire, a gold nanowire, a carbon nanowire, and a nickel nanowire.

The light diffusion layer may further include a light scatteringparticle, and the light scattering particle may include at least one oftitanium oxide (TiO₂), aluminum oxide (Al₂O₃), indium oxide (In₂O₃),zinc oxide (ZnO), tin oxide (SnO₂), and silica.

The display device may further include a first bank and a second bank onthe substrate and arranged to be spaced apart from each other, whereinthe first bank may overlap with the first electrode, and the second bankmay overlap with the second electrode.

The first insulating layer may include a first opening exposing at leasta portion of the first electrode, and a second opening exposing at leasta portion of the second electrode, and the first opening may overlapwith the first bank, and the second opening may overlap with the secondbank.

A space may be defined between the light emitting element and the firstinsulating layer.

The display device may further include a first insulating pattern on thelight emitting element, wherein the first insulating pattern may exposethe first end portion and the second end portion of the light emittingelement.

The display device may further include a second insulating pattern onthe third electrode, wherein the second insulating pattern may bearranged both on a region including the first end portion of the lightemitting element and on the third electrode, and may cover an end of thethird electrode on the light emitting element.

The display device may further include a bank pattern on the substrateand surrounding the light emitting element in a plane view.

The light diffusion layer may overlap with the light emitting elementand may not overlap with the bank pattern.

The display device may further include a wavelength conversion layer onthe light emitting element and including a wavelength conversionparticle, wherein the wavelength conversion particle may include aquantum dot.

A display device according to one or more embodiments of the presentinvention includes: a first pixel in a display area, wherein the firstpixel includes a substrate; a first electrode and a second electrodearranged to be spaced apart from each other on the substrate; a firstinsulating layer on the substrate and exposing a portion of the firstelectrode and a portion of the second electrode; a light emittingelement on the first insulating layer, located between the firstelectrode and the second electrode, and including a first end portionand a second end portion; a third electrode on the substrate andelectrically connected to the first electrode and the first end portion;a fourth electrode on the substrate and electrically connected to thesecond electrode and the second end portion; a second insulating layeron the substrate and covering the light emitting element, the thirdelectrode, and the fourth electrode; a light diffusion layer on thesecond insulating layer and including a light diffusion particle; and afirst wavelength conversion layer on the substrate and including a firstwavelength conversion particle, wherein the light emitting element emitslight of a first color, and the first wavelength conversion particleconverts the light of the first color into light of a second color.

The display device may further include a second pixel in the displayarea and arranged adjacent to the first pixel, wherein the second pixelmay include a second wavelength conversion layer including a secondwavelength conversion particle, and the second wavelength conversionparticle may convert the light of the first color into light of a thirdcolor.

The display device may further include a third pixel in the display areaand arranged adjacent to the first pixel and the second pixel, whereinthe third pixel may include a light scattering particle, and the lightscattering particle may include at least one of titanium oxide (TiO₂),aluminum oxide (Al₂O₃), indium oxide (In₂O₃), zinc oxide (ZnO), tinoxide (SnO₂), and silica.

The display device may further include a bank pattern between the firstpixel and the second pixel, wherein the light diffusion layer may notoverlap with the bank pattern.

The light diffusion layer may be between the light emitting element andthe first wavelength conversion layer.

The display device may further include a passivation layer covering thefirst wavelength conversion layer, wherein the light diffusion layer maybe on the passivation layer.

A display device according to one or more embodiments of the presentinvention includes: a substrate; a first electrode and a secondelectrode arranged to be spaced apart from each other on the substrate;a first insulating layer on the substrate; a light emitting element onthe first insulating layer, located between the first electrode and thesecond electrode, and including a first end portion and a second endportion; a third electrode on the substrate and electrically connectedto the first electrode and the first end portion; a fourth electrode onthe substrate and electrically connected to the second electrode and thesecond end portion; a second insulating layer on the substrate andcovering the light emitting element, the third electrode, and the fourthelectrode; and a wavelength conversion layer on the second insulatinglayer and including a wavelength conversion particle and a lightdiffusion particle, wherein the light diffusion particle includes atleast one of a silver nanowire, a gold nanowire, a carbon nanowire, anda nickel nanowire.

Aspects of other embodiments are included in the detailed descriptionand drawings.

According to an aspect of embodiments of the present invention, a lightdiffusion layer is disposed on a light emitting element to provide adisplay device with improved uniformity of light emitted withoutdeteriorated optical characteristics.

However aspects and effects of embodiments of the present invention arenot limited by those discussed above, and further various effects areincluded in the present specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are perspective views of a light emitting elementaccording to embodiments.

FIG. 2 is a top plan view schematically showing a display deviceaccording to an embodiment.

FIGS. 3A and 3B are circuit diagrams showing a pixel according toembodiments.

FIG. 4 is a circuit diagram showing a pixel according to anotherembodiment.

FIG. 5 is a top plan view of a pixel according to an embodiment.

FIG. 6 is a schematic cross-sectional view of a pixel taken along theline I-I′ of FIG. 5.

FIG. 7A is a cross-sectional view taken along the line II-II′ of FIG. 5.

FIG. 7B is a cross-sectional view of another embodiment, taken along aline corresponding to the line II-II′ of FIG. 5.

FIG. 8 is an enlarged cross-sectional view of a portion of a lightdiffusion layer according to an embodiment.

FIG. 9 is an enlarged cross-sectional view of a portion of a lightdiffusion layer according to another embodiment.

FIGS. 10 to 12 are cross-sectional views of a pixel according to variousembodiments, taken along a line corresponding to the line II-II′ of FIG.5.

FIG. 13 is a top plan view of a pixel unit according to an embodiment.

FIG. 14 is a cross-sectional view taken along the line III-III′ of FIG.13.

FIG. 15 is a cross-sectional view showing an embodiment in which a lightdiffusion layer of FIG. 14 is disposed on a light conversion layer,taken along a line corresponding to the line III-III′ of FIG. 13.

FIG. 16 is a cross-sectional view of an embodiment in which a lightdiffusion layer of FIG. 14 is not disposed and a light conversion layerincludes a light diffusion particle, taken along a line corresponding tothe line III-III′ of FIG. 13.

DETAILED DESCRIPTION

Aspects and features of the present invention, and implementationmethods thereof will be clarified through the following exampleembodiments described with reference to the accompanying drawings. Thepresent invention may, however, be embodied in different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the presentinvention to those skilled in the art. Further, the present invention isdefined by the scope of the claims.

It is to be understood that when an element or a layer is referred to asbeing “on” another element or layer, it may be directly on anotherelement or layer, or one or more intervening elements or layers may alsobe present.

Although the terms “first,” “second,” and the like are used to describevarious constituent elements, these constituent elements are not limitedby these terms. These terms are used to distinguish one constituentelement from another constituent element. Therefore, “first” constituentelements described below may be second constituent elements within thetechnical spirit of the present invention. When explaining the singular,unless explicitly described to the contrary, it may be interpreted asthe plural meaning.

Meanwhile, some of the elements not directly related to the features ofthe present invention in the drawing may be omitted in order to clearlyillustrate the present invention. In addition, some of the elements inthe drawings may be shown in somewhat exaggerated sizes, ratios, and thelike. For the same or similar constituent elements throughout thedrawings, the same reference numerals and symbols may be provided evenif they are displayed on different drawings, and duplicate descriptionsmay be omitted.

It is to be further understood that the terms “comprises” and/or“comprising” used herein specify the presence of stated features orcomponents, but do not preclude the presence or addition of one or moreother features or components.

In embodiments set forth herein, when a layer, area, or component isconnected to another layer, area, or component, the layers, areas, orcomponents may be directly connected to each other, and the layers,areas, or components may also be indirectly connected to each other withanother layer, area, or component therebetween.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments of theinventive concept belong. It is to be further understood that terms,such as those defined in commonly-used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and will not be interpreted in anidealized or overly formal sense unless expressly so defined herein.

Herein, referring to the drawings, some example embodiments of thepresent invention will be described in further detail.

FIGS. 1A and 1B are perspective views of a light emitting elementaccording to embodiments.

Referring to FIGS. 1A and 1B, a light emitting element LD according toan embodiment of the present invention may include a first semiconductorlayer 11, a second semiconductor layer 13, and an active layer 12interposed between the first and second semiconductor layers 11 and 13.For example, the light emitting element LD may be implemented as alaminate in which the first semiconductor layer 11, the active layer 12,and the second semiconductor layer 13 are sequentially stacked.

According to an example embodiment of the present invention, the lightemitting element LD may be provided in a rod shape extending in adirection. When an extending direction of the light emitting element LDis referred to as a length direction, the light emitting element LD mayhave a first end portion EP1 and a second end portion EP2 in the lengthdirection.

In an embodiment of the present invention, one of the first and secondsemiconductor layers 11 and 13 may be disposed in the first end portionEP1, and the other of the first and second semiconductor layers 11 and13 may be disposed in the second end portion EP2. For example, the firstsemiconductor layer 11 may be disposed in the first end portion EP1, andthe second semiconductor layer 13 may be disposed in the second endportion EP2.

In an example embodiment of the present invention, the light emittingelement LD may be provided in a rod shape. Here, “rod-shaped” refers torod-like shapes or bar-like shapes that are long in the length direction(i.e., having an aspect ratio greater than 1), such as a circular columnor a polygonal column. For example, a length of the light emittingelement LD may be greater than a diameter thereof. However, the presentinvention is not limited thereto. For example, a light emitting elementmay have a core-shell structure.

In an embodiment, the light emitting element LD may be small enough tohave a diameter and/or a length such as microscale or nanoscale. Forexample, the diameter of the light emitting element LD may be 600 nm orless, and the length of the light emitting element LD may be 4 μm orless. However, a size of the light emitting element LD is not limitedthereto. For example, the size of the light emitting element LD may bechanged to meet a requirement condition.

In an embodiment, the first semiconductor layer 11 may include at leastone n-type semiconductor layer. For example, the first semiconductorlayer 11 may include at least one of semiconductor materials such asInAlGaN, GaN, AlGaN, InGaN, AlN and InN, and may include a semiconductorlayer doped with a first dopant such as Si, Ge, Sn, and the like.

However, the material constituting the first semiconductor layer 11 isnot limited thereto, and the first semiconductor layer 11 may be formedof various materials.

The active layer 12 may be formed on the first semiconductor layer 11and may be formed with a single or multiple quantum well structure. Inan embodiment, the active layer 12 may emit light having a wavelength of400 nm to 900 nm, and may have a double hetero structure. According toan example embodiment of the present invention, a cladding layer (notshown) doped with a dopant may be formed on and/or under the activelayer 12. For example, the cladding layer may be formed of an AlGaNlayer or an InAlGaN layer. In addition, materials such as AlGaN andAlInGaN may constitute the active layer 12, and various materials mayconstitute the active layer 12.

When an electric field of a certain (e.g., predetermined) voltage ormore is applied to opposite ends of the light emitting element LD, thelight emitting element LD emits light by forming electron-hole pairs inthe active layer 12. The light emitting element LD may be used as alight source of any of various light emitting devices including thepixel of the display device by controlling light emitting of lightemitting element LD using this principle.

The second semiconductor layer 13 may be provided on the active layer 12and may include a semiconductor layer of a different type from the firstsemiconductor layer 11. For example, the second semiconductor layer 13may include at least one p-type semiconductor layer. For example, thesecond semiconductor layer 13 may include at least one semiconductormaterial of InAlGaN, GaN, AlGaN, InGaN, AlN, and InN, and may include asemiconductor layer doped with a second dopant, such as Mg. However, thematerial constituting the second semiconductor layer 13 is not limitedthereto, and various materials may constitute the second semiconductorlayer 13.

According to an embodiment of the present invention, the light emittingelement LD may further include other phosphor layers, active layers,semiconductor layers, and/or electrode layers on and/or under each layerin addition to the first semiconductor layer 11, the active layer 12,and the second semiconductor layer 13 described above.

In an embodiment, the light emitting element LD may further include atleast one electrode layer disposed on an end (e.g., an upper surface) ofthe second semiconductor layer 13 or on an end (e.g., a lower surface)of the first semiconductor layer 11. For example, the light emittingelement LD may include an electrode layer 15 disposed on an end of thesecond semiconductor layer 13, as shown in FIG. 1B. In an embodiment,the electrode layer 15 may be an ohmic contact electrode, but is notlimited thereto. In addition, the electrode layer 15 may include a metalor a metal oxide. For example, the electrode layer 15 may be formed byusing alone or in combination chromium (Cr), titanium (Ti), aluminum(Al), gold (Au), nickel (Ni), ITO, and oxides or alloys thereof, but thepresent invention is not limited thereto. In addition, according to anembodiment, the electrode layer 15 may be substantially transparent ortranslucent. Accordingly, light generated from the light emittingelement LD may be transmitted through the electrode layer 15 and emittedto the outside of the light emitting element LD.

In addition, the light emitting element LD may further include aninsulating film 14. However, according to an embodiment of the presentinvention, the insulating film 14 may be omitted or may be provided tocover only a portion of the first semiconductor layer 11, the activelayer 12, and the second semiconductor layer 13. For example, theinsulating film 14 may be provided at a portion except for opposite endsof the light emitting element LD such that opposite ends of the lightemitting element LD may be exposed.

For better understanding and ease of description, FIGS. 1A and 1B show astate in which a part of the insulating film 14 is removed, and, in anembodiment, all of side surface of the light emitting element LD may beactually surrounded by the insulating film 14.

According to an embodiment of the present invention, the insulating film14 may include a transparent insulating material. For example, theinsulating film 14 may include at least one insulating material of SiO₂,Si₃N₄, Al₂O₃, and TiO₂, but is not limited thereto. The insulating film14 may include various insulating materials.

The insulating film 14 may prevent or substantially prevent an electricshort which may occur when the active layer 12 contacts conductivematerials other than the first semiconductor layer 11 and the secondsemiconductor layer 13. In addition, it is possible to improve thelifetime and the efficiency by forming the insulating film 14 tominimize or reduce surface defects of the light emitting element LD. Inaddition, when a plurality of light emitting elements LD are closelydisposed, the insulating film 14 may prevent or substantially preventunwanted shorting that may occur between light emitting elements LD.

The type, structure, shape, and the like of the light emitting elementaccording to embodiments of the present invention may be variouslychanged.

FIG. 2 is a top plan view schematically showing a display deviceaccording to an embodiment.

Referring to FIGS. 1A to 2, a display device 1000 may include asubstrate SUB and a plurality of pixels PXL provided on the substrateSUB. The display device 1000 may include a display area DA in which animage is displayed and a non-display area NDA excluding the display areaDA.

The display area DA may be an area where the pixels PXL are provided.The non-display area NDA may be an area where drivers for driving thepixels PXL and various lines (not shown) for connecting the drivers andthe pixels PXL are provided.

The display area DA may have various shapes. For example, the displayarea DA may have any of various shapes, such as a closed polygonincluding sides consisting of a straight line, a circle, an ellipse,etc. including sides consisting of a curved line, and a semicircle, asemi-ellipse, etc. including sides consisting of a straight line and acurved line.

When the display area DA includes a plurality of areas, each area mayalso have various shapes, such as a closed polygon including sides of astraight line, a semicircle, a semi-ellipse, etc. including sides of acurved line, and an ellipse. In addition, a plurality of areas may havethe same or different areas.

In an example embodiment of the present invention, a case in which thedisplay area DA is provided as an area having a quadrangular shapeincluding sides of a straight line will be described.

The non-display area NDA may be provided on at least one side of thedisplay area DA. In an example embodiment of the present invention, thenon-display area NDA may surround the display area DA.

The pixels PXL may be provided in the display area DA on the substrateSUB. Each of the pixels PXL may include at least one light emittingelement LD driven by a corresponding scan signal and data signal.

The pixels PXL may include the light emitting element emitting whitelight and/or color light. Each of the pixels PXL may emit one of red,green, and blue colors, but is not limited thereto. For example, each ofthe pixels PXL may emit one of cyan, magenta, yellow, and white colors.

The pixels PXL may include a first pixel PXL1 emitting light of a firstcolor, a second pixel PXL2 emitting light of a second color differentfrom the first color, and a third pixel PXL3 emitting light of a thirdcolor different from the first color and the second color. At least onethe first pixel PXL1, the second pixel PXL2, and the third pixel PXL3,which are disposed adjacent to each other, may constitute one pixel unitPXU capable of emitting light of various colors.

According to an embodiment, the first pixel PXL1 may be a red pixelemitting red light, the second pixel PXL2 may be a green pixel emittinggreen light, and the third pixel PXL3 may be a blue pixel emitting bluelight. In an embodiment, the first pixel PXL1, the second pixel PXL2,and the third pixel PXL3 may emit light of the first color, the secondcolor, and the third color, respectively, by including a light emittingelement of the first color, a light emitting element of the secondcolor, and a light emitting element of the third color as light sources.In another embodiment, the first pixel PXL1, the second pixel PXL2, andthe third pixel PXL3 may emit light of the first color, the secondcolor, and the third color, respectively, by including light emittingelements of the same color as each other and including light conversionlayers of different colors disposed on each of the light emittingelements.

However, the color, type, and/or number of the pixels PXL constitutingeach pixel unit PXU are not particularly limited.

The pixels PXL may be provided in plural and arranged in rows andcolumns in a matrix form in a first direction DR1 and a second directionDR2 crossing the first direction DR1. However, the arrangement of thepixels PXL is not particularly limited, and may be arranged in variousforms.

A driver may provide a signal to each of the pixels PXL through a lineunit not shown, thereby controlling a driving of each of the pixels PXL.FIG. 2 omits the line unit for better understanding and ease ofdescription.

The driver may include a scan driver SDV providing a scan signal to thepixels PXL through a scan line, an emission driver EDV providing anemission control signal to the pixels PXL through an emission controlline, a data driver DDV providing a data signal to the pixels PXLthrough a data line, and a timing controller (not shown). The timingcontroller may control the scan driver SDV, the emission driver EDV, anddata driver DDV.

In an embodiment, each of the pixels PXL may be formed of an activepixel. However, the type, structure, and/or driving method of the pixelsPXL applicable to the present invention are not particularly limited.

FIGS. 3A and 3B are circuit diagrams showing a pixel according toembodiments. Particularly, FIGS. 3A and 3B show an example of pixelsconstituting a light emitting display panel of an active type.

Referring to FIG. 3A, the pixel PXL may include at least one lightemitting element LD and a pixel driving circuit DC connected to thelight emitting element LD for driving the light emitting element LD.

A first electrode (e.g., anode) of the light emitting element LD may beconnected to a first driving power supply VDD via the pixel drivingcircuit DC, and a second electrode (e.g., cathode) of the light emittingelement LD may be connected to a second driving power supply VSS.

The first driving power supply VDD and the second driving power supplyVSS may have different potentials. For example, the second driving powersupply VSS may have a lower potential than the first driving powersupply VDD by a threshold voltage or more of the light emitting elementLD.

The light emitting element LD may emit light at a luminancecorresponding to the driving current controlled by the pixel drivingcircuit DC.

FIG. 3A shows an example embodiment in which only one light emittingelement LD is included in the pixel PXL, but the present invention isnot limited thereto. For example, the pixel PXL may include a pluralityof light emitting elements that are connected in parallel and/or inserial connected to each other.

According to an embodiment of the present invention, the pixel drivingcircuit DC may include a first transistor M1, a second transistor M2,and a storage capacitor Cst. However, the structure of the pixel drivingcircuit DC is not limited to an embodiment shown in FIG. 3A. Accordingto an embodiment, the pixel PXL may further include a pixel sensingcircuit (not shown). The pixel sensing circuit may measure a value ofthe driving current of each pixel PXL, and may transmit the measuredvalue to an external circuit (e.g., timing controller) to compensate foreach pixel PXL.

A first electrode of the first transistor M1 (or switching transistor)may be connected to a data line DL, and a second electrode thereof maybe connected to a first node N1. Here, the first electrode and thesecond electrode of the first transistor M1 are different electrodes,and, for example, when the first electrode is a source electrode, thesecond electrode may be a drain electrode. The gate electrode of thefirst transistor M1 may be connected to a scan line SL.

The first transistor M1 may be turned on when a scan signal of a voltage(e.g., gate-on voltage) that may turn on the first transistor M1 fromthe scan line SL is provided, to electrically connect the data line DLand the first node N1. At this time, the data signal of thecorresponding frame may be supplied to the data line DL, such that thedata signal may be transferred to the first node N1. The data signaltransferred to the first node N1 may be stored in the storage capacitorCst.

A first electrode of a second transistor M2 (or driving transistor) maybe connected to the first power supply VDD and a second electrodethereof may be electrically connected to the first electrode of thelight emitting element LD (e.g. anode). The gate electrode of the secondtransistor M2 may be connected to the first node N1. The secondtransistor M2 may control an amount of driving current supplied to thelight emitting elements LD in response to a voltage of the first nodeN1.

One electrode of the storage capacitor Cst may be connected to the firstpower supply VDD, and the other electrode thereof may be connected tothe first node N1. Such a storage capacitor Cst may be charged with avoltage corresponding to the data signal supplied to the first node N1,and may maintain the charged voltage until the data signal of the nextframe is supplied.

For better understanding and ease of description, FIG. 3A shows adriving circuit DC with a relatively simple structure including thefirst transistor M1 for transferring the data signal to the pixel PXL,the storage capacitor Cst for storing the data signal, and the secondtransistor M2 for supplying the driving current corresponding to thedata signal to the light emitting element LD.

However, the present invention is not limited thereto, and the structureof the driving circuit DC may be variously modified. For example, thedriving circuit DC may further include at least one transistor, such asa transistor for compensating for a threshold voltage of the secondtransistor M2, a transistor for initializing the first node N1, and/or atransistor for controlling a light emitting time of the light emittingelement LD, and the like, and other circuit elements such as a boostingcapacitor for boosting a voltage of the first node N1, and the like.

In addition, transistors included in the driving circuit DC, forexample, first and second transistors M1 and M2 are all shown as P-typetransistors in FIG. 3A, but the present invention is not limitedthereto. That is, at least one of the first and second transistors M1and M2 included in the driving circuit DC may be an N-type transistor.

For example, referring to FIG. 3B, the first and second transistors M1and M2 of the driving circuit DC may be implemented as N-typetransistors. The driving circuit DC shown in FIG. 3B may be similar tothe driving circuit DC shown in FIG. 3A in configuration or operationexcept for a change of a connection position of some constituentelements due to a change in a type of a transistor. Therefore, adetailed description thereof will be omitted.

FIG. 4 is a circuit diagram showing a pixel according to anotherembodiment.

Referring to FIG. 4, the pixel PXL according to another embodiment ofthe present invention may include a light emitting element LD, first toseventh transistors T1, T2, T3, T4, T5, T6, and T7, and a storagecapacitor Cst.

The first electrode (e.g., anode) of the light emitting element LD maybe connected to the first transistor T1 via a sixth transistor T6, andthe second electrode (e.g., cathode) of the light emitting element LDmay be connected to the second driving power supply VSS. The lightemitting element LD may emit light at a certain (e.g., predetermined)luminance corresponding to an amount of current supplied from the firsttransistor Ti.

One electrode of the first transistor T1 (or driving transistor) may beconnected to the first driving power supply VDD via a fifth transistorT5, and the other electrode may be connected to the first electrode ofthe light emitting element LD via the sixth transistor T6. The firsttransistor T1 may control an amount of current flowing from the firstdriving power supply VDD to the second driving power supply VSS via thelight emitting element LD corresponding to a voltage of the first nodeN1 which is a gate electrode.

The second transistor T2 (or switching transistor) may be connectedbetween the data line DL and an electrode of the first transistor T1.The gate electrode of the second transistor T2 may be connected to thescan line SL. The second transistor T2 may be turned on when a scansignal of a gate-on voltage is supplied to the scan line SL, therebyelectrically connecting the data line DL and an electrode of the firsttransistor Ti.

A third transistor T3 may be connected between another electrode of thefirst transistor T1 and the first node N1. A gate electrode of the thirdtransistor T3 may be connected to the scan line SL. The third transistorT3 may be turned on when a scan signal of a gate-on voltage is suppliedto the scan line SL, thereby electrically connecting another electrodeof the first transistor T1 and the first node N1.

A fourth transistor T4 may be connected between the first node N1 and aninitialization power supply Vint. A gate electrode of the fourthtransistor T4 may be connected to a previous scan line SL-1. The fourthtransistor T4 may be turned on when a scan signal of a gate-on voltageis supplied to the previous scan line SL-1, thereby supplying a voltageof the initialization power supply Vint to the first node N1. Here, theinitialization power supply Vint may be set to a lower voltage than thedata signal.

The fifth transistor T5 may be connected between the first driving powersupply VDD and an electrode of the first transistor Ti. A gate electrodeof the fifth transistor T5 may be connected to an i-th emission controlline EL. The fifth transistor T5 may be turned on when the emissioncontrol signal of a gate-on voltage is supplied to the i-th emissioncontrol line EL, and may be turned off in other cases.

The sixth transistor T6 may be connected between another electrode ofthe first transistor T1 and the first electrode of the light emittingelement LD. A gate electrode of the sixth transistor T6 may be connectedto the emission control line EL. The sixth transistor T6 may be turnedon when an emission control signal of a gate-on voltage is supplied tothe emission control line EL, and may be turned off in other cases.

A seventh transistor T7 may be connected between the initializationpower supply Vint and the first electrode of the light emitting elementLD. A gate electrode of the seventh transistor T7 may be connected to anext scan line SL+1. The seventh transistor T7 may be turned on when ascan signal of a gate-on voltage is supplied to the next scan line SL+1,thereby supplying a voltage of the initialization power supply Vint tothe first electrode of the light emitting element LD.

The storage capacitor Cst may be connected between the first powersupply VDD and the first node N1. The storage capacitor Cst may store avoltage corresponding to the data signal and the threshold voltage ofthe first transistor Ti.

The transistors included in the driving circuit DC, for example, thefirst to seventh transistors T1, T2, T3, T4, T5, T6, and T7 are allshown as P-type transistors in FIG. 4, but the present invention is notlimited thereto. For example, at least one of the first to seventhtransistors T1, T2, T3, T4, T5, T6, and T7 may be an N-type transistor.

FIG. 5 is a top plan view of a pixel according to an embodiment; FIG. 6is a schematic cross-sectional view of a pixel taken along the line I-I′of FIG. 5; and FIG. 7A is a cross-sectional view taken along the lineII-II′ of FIG. 5. FIG. 7B is a cross-sectional view of anotherembodiment, taken along a line corresponding to the line II-II′ of FIG.5.

Herein, for better understanding and ease of description, each electrodeis shown as a single electrode layer, but the present invention is notlimited thereto. In an embodiment of the present invention, “formedand/or provided in the same layer” may mean formed in the same process.

For better comprehension and ease of description, a plurality of lightemitting elements LD are shown to be arranged in the first direction DR1in FIG. 5, but the arrangement of the light emitting element LD is notlimited thereto. For example, the light emitting element LD may bearranged in a diagonal direction between first and second electrodesRFE1 and RFE2.

Referring to FIGS. 1A to 7B, a display device according to an exemplaryembodiment of the present invention may include a substrate SUB, a banklayer BNKL, first and second electrodes RFE1 and RFE2, a firstinsulating layer INS1, a light emitting element LD, third and fourthelectrodes CTE1 and CTE2, a second insulating layer INS2, and a lightdiffusion layer HZL.

The substrate SUB may be a rigid substrate or a flexible substrate, andthe material and physical properties thereof are not particularlylimited. For example, the substrate SUB may be a hard substrate formedof glass or tempered glass, or a flexible substrate formed of a thinfilm of plastic or metallic material. In addition, the substrate SUB maybe a transparent substrate, but is not limited thereto. For example, thesubstrate SUB may be a semi-transparent substrate, an opaque substrate,or a reflective substrate.

The bank layer BNKL may be provided on the substrate SUB. In anembodiment, the bank layer BNKL may include a first bank BNK1 and asecond bank BNK2.

The first bank BNK1 and the second bank BNK2 may be provided on thesubstrate SUB. A space in which the light emitting element LD isdisposed may be provided between the first bank BNK1 and the second bankBNK2. In an embodiment, the first bank BNK1 and the second bank BNK2 maybe spaced apart from each other in the first direction DR1 on thesubstrate SUB beyond a length of the light emitting element LD.

The first bank BNK1 and the second bank BNK2 may be made of aninsulating material including an organic material or an inorganicmaterial, but the material of the first bank BNK1 and the second bankBNK2 is not limited thereto.

In an embodiment, the first bank BNK1 and the second bank BNK2 may havea trapezoidal shape whose sides are inclined at certain (e.g.,predetermined) angles, but the shape of the first bank BNK1 and thesecond bank BNK2 is not limited thereto, and may be any of variousshapes, such as a semi-ellipse, a circle, a quadrangle shape, and thelike.

The first electrode RFE1 and the second electrode RFE2 may be disposedon the bank layer BNKL. In an embodiment, the first electrode RFE1 andthe second electrode RFE2 may be provided on corresponding first andsecond banks BNK1 and BNK2, respectively. For example, the firstelectrode RFE1 may be provided on the first bank BNK1 and the secondelectrode RFE2 may be provided on the second bank BNK2.

In an embodiment, the first electrode RFE1 and the second electrode RFE2may be disposed with a substantially uniform thickness along a surfaceof the first bank BNK1 and the second bank BNK2, and the first electrodeRFE1 and the second electrode RFE2 may be provided to correspond to theshapes of the first bank BNK1 and the second bank BNK2. For example, thefirst electrode RFE1 may have a shape corresponding to a slope of thefirst bank BNK1, and the second electrode RFE2 may have a shapecorresponding to a slope of the second bank BNK2.

The first electrode RFE1 and the second electrode RFE2 may be spacedapart from each other in the first direction DR1 with a light emittingelement LD therebetween on the substrate SUB, and may be provided toextend in the second direction DR2 crossing the first direction DR1.

In an embodiment, the first electrode RFE1 may be disposed adjacent tothe first end portion EP1 of each light emitting element LD, and may beelectrically connected to each light emitting element LD through a thirdelectrode CTE1 (or first contact electrode). The second electrode RFE2may be disposed adjacent to the second end portion EP2 of each lightemitting element LD, and may be electrically connected to each lightemitting element LD through a fourth electrode CTE2 (or second contactelectrode).

In an embodiment, the first electrode RFE1 and the second electrode RFE2may be disposed on the same plane and may have the same height. Forexample, when the first electrode RFE1 and the second electrode RFE2have the same height, one light emitting element LD may be more stablyconnected to each of the first electrode RFE1 and the second electrodeRFE2.

The first electrode RFE1 and the second electrode RFE2 may be made of aconductive material. The conductive material may include any of metals,such as Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Ti, and alloys thereof.

In an embodiment, the first electrode RFE1 and the second electrode RFE2may be formed of a single layer, but are not limited thereto, and may beformed of a multilayer. For example, the first electrode RFE1 and thesecond electrode RFE2 may further include a capping layer (not shown)made of a transparent conductive material. The capping layer may bedisposed to cover the first electrode RFE1 and second electrode RFE2 toprevent or substantially prevent damage to the first and secondelectrodes RFE1 and RFE2 that may occur during a manufacturing processof the display device.

Here, a material of the first electrode RFE1 and the second electrodeRFE2 is not limited to the materials described above. For example, thefirst electrode RFE1 and the second electrode RFE2 may be made of aconductive material with a certain (e.g., predetermined) reflectance.When the first electrode RFE1 and the second electrode RFE2 are made ofa conductive material with a certain (e.g., predetermined) reflectance,the light emitted from opposite ends EP1 and EP2 of the light emittingelement LD may proceed in a direction (e.g., a third direction DR3) inwhich the image is displayed.

In an embodiment, since the first electrode RFE1 and second electrodeRFE2 has a shape corresponding to a shape of the first bank BNK1 and thesecond bank BNK2, the light emitted from opposite ends EP1 and EP2 ofthe light emitting elements LD may be reflected by the first electrodeRFE1 and the second electrode RFE2 to further proceed to the thirddirection DR3. Therefore, an emission efficiency of the display devicemay be improved.

One of the first and second electrodes RFE1 and RFE2 may be an anode andthe other electrode thereof may be a cathode. For example, the firstelectrode RFE1 may be the cathode and the second electrode RFE2 may bethe anode. However, the present invention is not limited thereto, andthe first electrode RFE1 may be an anode and the second electrode RFE2may be a cathode.

For better understanding and ease of description, the first and secondelectrodes RFE1 and RFE2 are shown to be directly provided on thesubstrate SUB, but are not limited thereto. For example, a constituentelement may be further provided for driving the display device as apassive matrix or active matrix between the first and second electrodesRFE1 and RFE2 and the substrate SUB.

In an embodiment, the first electrode RFE1 may be connected to a firstconnecting line CNL1, and the second electrode RFE2 may be connected toa second connecting line CNL2. According to an example embodiment, thefirst connecting line CNL1 may be provided integrally with the firstelectrode RFE1, and the second connecting line CNL2 may be providedintegrally with the second electrode RFE2.

The first connecting line CNL1 may be electrically connected to a firstpower line (not shown) through a first hole CT1. The second connectingline CNL2 may be electrically connected to a second power line DVLthrough a second hole CT2. The light emitting element LD may emit lightin response to a driving signal applied through the first connectingline CNL1 and the second connecting line CNL2.

Referring to FIG. 3A, the first electrode RFE1 and the second electrodeRFE2 may be electrically connected to the driving circuit DC or thesecond driving power supply VSS through the first connecting line CNL1and the second connecting line CNL2. The first electrode RFE1 may beelectrically connected to the second driving power supply VSS, and thesecond electrode RFE2 may be electrically connected to the drivingcircuit DC. The first electrode RFE1 and the second electrode RFE2 maybe connected to the first end portion EP1 and the second end portion EP2of the light emitting element LD to provide a driving signal to thelight emitting element LD, and the light emitting element LD may emitlight of a certain (e.g., predetermined) luminance in response to thedriving current provided from the driving circuit DC.

The first insulating layer INS1 may be provided on the first electrodeRFE1 and the second electrode RFE2. In an embodiment, the firstinsulating layer INS1 is provided entirely on the substrate SUB to coverthe first and second banks BNK1 and BNK2 and the first and secondelectrodes RFE1 and RFE2 described above. In addition, the firstinsulating layer INS1 may be disposed along a surface of the substrateSUB in which the first and second banks BNK1 and BNK2 and the first andsecond electrodes RFE1 and RFE2 are not disposed.

The first insulating layer INS1 may be provided between the substrateSUB and each of the light emitting elements LD. In an exampleembodiment, the first insulating layer INS1 may be an inorganicinsulating layer made of an inorganic material. In an embodiment, thefirst insulating layer INS1 may be disposed with a substantially uniformthickness along the surface of the substrate SUB and the first andsecond electrodes RFE1 and RFE2, and a spacing or space VD may bedefined between the first insulating layer INS1 and the light emittingelement LD.

In some embodiments, the first insulating layer INS1 may include anorganic insulating layer made of an organic material. As shown in FIG.7B, each pixel PXL′ may include a first insulating layer INS1′ includingan organic insulating layer. In an embodiment, the first insulatinglayer INS1′ may fill a space between the substrate SUB and the lightemitting element LD to stably support the light emitting element LD.

In an embodiment, the first insulating layer INS1 may include a firstopening OP1 and a second opening OP2. The first opening OP1 and thesecond opening OP2 may expose at least a portion of the first electrodeRFE1 and the second electrode RFE2.

The first and second openings OP1 and OP2 may be formed on thecorresponding first and second banks BNK1 and BNK2, respectively. Forexample, the first opening OP1 may be formed on the first bank BNK1, andthe second opening OP2 may be formed on the second bank BNK2.

The first opening OP1 and the second opening OP2 may have a thicknessand/or depth corresponding to a thickness of the first insulating layerINS1. That is, the first opening OP1 and the second opening OP2 maycompletely pass through the first insulating layer INS1 in thecorresponding region. Thus, the first and second electrodes RFE1 andRFE2 may be exposed to the outside to contact third and fourthelectrodes CTE1 and CTE2 described below.

The third electrode CTE1 and the fourth electrode CTE2 may be providedon the first insulating layer INS1 and the light emitting element LD.

The third electrode CTE1 and the fourth electrode CTE2 may be partiallyoverlapped with one of opposite ends EP1 and EP2 of each of the lightemitting elements LD. For example, the third electrode CTE1 may bepartially overlapped with the first end portion EP1 of each of the lightemitting elements LD, and the fourth electrode CTE2 may be partiallyoverlapped with the second end portion EP2 of each of the light emittingelements LD.

The third electrode CTE1 may cover the first electrode RFE1 and overlapwith the first electrode RFE1 in a plane view. The third electrode CTE1may be electrically connected to the first electrode RFE1 through thefirst opening OP1 of the first insulating layer INS1.

The fourth electrode CTE2 may cover the second electrode RFE2 andoverlap with the second electrode RFE2 in a plane view. The fourthelectrode CTE2 may be electrically connected to the second electrodeRFE2 through the second opening OP2 of the first insulating layer INS1.

Each of the third and fourth electrodes CTE1 and CTE2 may be made of atransparent conductive material. For example, the transparent conductivematerial may include ITO, IZO, ITZO, and the like. When the third andfourth electrodes CTE1 and CTE2 are made of a transparent conductivematerial and light emitted from the light emitting element LD proceedsin the third direction DR3, a loss may be reduced. However, thematerials of third and fourth electrodes CTE1 and CTE2 are not limitedto the materials described above.

In an embodiment, the third and fourth electrodes CTE1 and CTE2 may beprovided on the same plane. In an embodiment, the third and fourthelectrodes CTE1 and CTE2 may be formed concurrently (e.g.,simultaneously). However, the present invention is not limited thereto,and, in an embodiment, the third and fourth electrodes CTE1 and CTE2 maybe provided on different planes. In an embodiment, an insulating patternmay be further disposed on one of the third and fourth electrodes CTE1and CTE2, and the other electrode thereof may be disposed on theinsulating pattern.

A bank pattern BNKP may be provided on the substrate SUB. In anembodiment, the bank pattern BNKP may be disposed on the firstinsulating layer INS1. In another embodiment, the bank pattern BNKP maybe directly disposed on the substrate SUB to contact the substrate SUB.

In an embodiment, the bank pattern BNKP may be disposed along a boundaryof each pixel PXL in a plane view. In other words, the light emittingelement LD may be surrounded by the bank pattern BNKP disposed along theboundary of each pixel PXL, and each pixel PXL may be defined by thebank pattern BNKP. In an embodiment, the bank pattern BNKP may beintegrally connected and disposed as shown in FIG. 5.

In an embodiment, the bank pattern BNKP may have a cross-section of atrapezoidal shape that is narrower upwards, such as the first bank BNK1and the second bank BNK2, but is not limited thereto. In anotherembodiment, the bank pattern BNKP may have a curved surface having across-section such as a semicircular or semi-elliptical shape narrowerupwards. However, in an embodiment of the present invention, the shapeand/or inclination of the bank pattern BNKP is not particularly limited,and may be variously modified.

The bank pattern BNKP may prevent or substantially prevent light leakagefrom occurring between adjacent pixels PXL. In addition, the bankpattern BNKP may prevent or substantially prevent a solution includingthe light emitting element LD from leaking to the adjacent pixel duringthe alignment of the light emitting element LD.

The second insulating layer INS2 may be provided on the third electrodeCTE1 and the fourth electrode CTE2. The second insulating layer INS2 mayprevent or substantially prevent the third electrode CTE1 and the fourthelectrode CTE2 from being exposed to the outside, thereby preventing orsubstantially preventing the third electrode CTE1 and the fourthelectrode CTE2 from corroding. The second insulating layer INS2 may alsofunction as a sealing layer to prevent or substantially prevent oxygenand moisture from penetrating into the light emitting element LD.

The second insulating layer INS2 may include an inorganic insulatinglayer made of an inorganic material or an organic insulating layer madeof an organic material. The second insulating layer INS2 may be formedof a single layer as shown in the drawing, but is not limited thereto,and may be formed of multiple layers.

In some embodiments, an overcoat layer (not shown) may be furtherprovided on the second insulating layer INS2. The overcoat layer may bea planarization layer that alleviates steps generated by variousstructures disposed thereunder.

The light diffusion layer HZL may be disposed on the second insulatinglayer INS2.

The light diffusion layer HZL may be a layer including light diffusionparticles for diffusion of light. The light emitted from the lightemitting element LD may be diffused by the light diffusion layer HZL tobe uniformly emitted to the outside of the pixel as a whole. Referringfurther to FIGS. 8 and 9, a further detailed description of the lightdiffusion layer HZL is provided.

FIG. 8 is an enlarged cross-sectional view of a portion of a lightdiffusion layer according to an embodiment; and FIG. 9 is an enlargedcross-sectional view of a portion of a light diffusion layer accordingto another embodiment.

Referring further to FIGS. 8 and 9 in addition to FIG. 7A, the lightdiffusion layer HZL may include at least one type of light diffusionparticle HZP.

For example, the light diffusion layer HZL may include a plurality oflight diffusion particles HZP dispersed in a certain (e.g.,predetermined) matrix material, such as a transparent resin. In anembodiment, the light diffusion layer HZL may include the lightdiffusion particle HZP, such as a nanowire (NW). The constitutingmaterial of the nanowire (NW) included in the light diffusion layer HZLmay be, for example, silver (Ag), gold (Au), carbon (C), nickel (Ni),and the like, but is not particularly limited.

The light diffusion particle HZP may diffuse at least some of thetransmitted light. For example, light emitted from the light emittingelement LD may transmit through the light diffusion layer HZL. Anoptical waveguide may be formed inside the light diffusion particle HZP,and an incident light L1 may be diffused in various directions insidethe light diffusion particle HZP. The diffused light may be emitted invarious directions as diffused light L2 from a surface of the lightdiffusion particle HZP. In other words, the incident light L1 emittedfrom the light emitting element LD, which is a point light source, maybe diffused by the light diffusion particle HZP, and may be emitted invarious directions along the surface of the light diffusion particle HZPlike light emitted from a planar light source.

In an embodiment, when the light diffusion layer HZL includes a metalnanowire, the light diffusion layer HZL may function as a conductivelayer. For example, when the light diffusion layer HLZ is directlydisposed on the third electrode CTE1 and the fourth electrode CTE2, ashort may occur due to the light diffusion layer HLZ. Thus, the lightdiffusion layer HZL may be disposed on the second insulating layer INS2,and may be isolated from other constituent elements by the secondinsulating layer INS2.

In some embodiments, the light diffusion layer HZL may further include alight scattering particle SCP as shown in FIG. 9.

The light scattering particle SCP may form optical interfaces withmatrix materials with different refractive indices from matrix materialsconstituting the light diffusion layer HZL. The light scatteringparticle SCP is not particularly limited as long as it is a materialcapable of scattering at least some of transmitted light. For example,the light scattering particle SCP may include oxide particles, such astitanium oxide (TiO₂), aluminum oxide (Al₂O₃), indium oxide (In₂O₃),zinc oxide (ZnO), tin oxide (SnO₂), and silica.

As described above, the light diffusion layer HZL may be disposed on thelight emitting element LD. The light diffusion layer HZL may diffuse thelight emitted from the light emitting element LD and may emit uniformlight as a whole. That is, the light diffusion layer HZL may improveuniformity of light emitted from each pixel PXL.

In addition, when the light diffusion layer HZL is disposed on thesecond insulating layer INS2, the light diffusion layer HZL may transmitsome of light that is totally reflected by a refractive index differencebetween the second insulating layer INS2 and air and is not emitted tothe outside. That is, the light diffusion layer HZL may improve thetransmittance of the constituted elements disposed on the light emittingelement LD, thereby improving a display luminance of the display device.

The display device according to an embodiment of the present inventionmay directly form the light diffusion layer HZL on the second insulatinglayer INS2 without a separate light diffusion member, such as a lightdiffusion film or a light diffusion sheet. As a result, a thickness ofthe display device may be made thinner.

Herein, further embodiments of the pixel will be described. In thefollowing embodiments, the same components as those of the previousembodiments are denoted by the same reference numerals, and thedescription thereof may be omitted or simplified.

FIGS. 10 to 12 are cross-sectional views of a pixel according to variousembodiments, taken along a line corresponding to the line II-II′ of FIG.5.

Referring to FIG. 10, in an embodiment, a first insulating pattern INSP1may be further disposed on the light emitting element LD.

The first insulating pattern INSP1 may be disposed on the light emittingelement LD, particularly the light emitting element LD aligned betweenthe first and second electrodes RFE1 and RFE2, and may expose the firstand second end portions EP1 and EP2 of the light emitting element LD.For example, the first insulating pattern INSP1 may be partiallydisposed on one area, including a central area of the light emittingelement LD, without covering the first and second end portions EP1 andEP2 of the light emitting element LD. The first insulating pattern INSP1may be formed with an independent pattern, but is not limited thereto.

The first insulating pattern INSP1 may stably fix the light emittingelement LD. For example, by forming the first insulating pattern INSP1on the light emitting element LD after an alignment of the lightemitting element LD is completed, it is possible to prevent orsubstantially prevent the light emitting element LD from deviating froman aligned position.

For example, the first insulating pattern INSP1 may include an organicinsulating layer made of an organic material.

When there is the space VD (see FIG. 7A) between the first insulatinglayer INS1 and the light emitting element LD before forming the firstinsulating pattern INSP1, the space VD may be filled in the process offorming the first insulating pattern INSP1. Accordingly, the lightemitting element LD may be more stably supported.

Referring to FIG. 11, in an embodiment, a second insulating patternINSP2 may be further disposed on the third electrode CTE1.

In an embodiment, the second insulating pattern INSP2 may be directlydisposed on the third electrode CTE1 to cover the third electrode CTE1.For example, the second insulating pattern INSP2 may be disposed on aregion including the first end portion EP1 of the light emitting elementLD and on the third electrode CTE1, and may cover an end of the thirdelectrode CTE1 on the light emitting element LD.

The second insulating pattern INSP2 may be interposed between the thirdelectrode CTE1 and the fourth electrode CTE2, thereby stably isolatingthe third and fourth electrodes CTE1 and CTE2. That is, by forming thesecond insulating pattern INSP2, short defects capable of occurringbetween third and fourth electrodes CTE1 and CTE2 may be effectivelyprevented. The second insulating pattern INSP2 may be formed on aportion of the light emitting element LD so as not to cover the secondend portions EP2 of the light emitting element LD.

Referring to FIG. 12, in an embodiment, a light diffusion layer HZLc maybe disposed only on a portion of the second insulating layer INS2, suchas not to be entirely disposed on the second insulating layer INS2. Thatis, the light diffusion layer HZLc may be patterned and disposed on thesecond insulating layer INS2.

For example, the light diffusion layer HZLc may be disposed to overlapwith the light emitting element LD, and may be disposed not to overlapwith the bank pattern BNKP surrounding the light emitting element LD.

When the light diffusion layer HZLc may be patterned and disposed, acolor mixture between adjacent pixels may be prevented or substantiallyprevented. Particularly, when the light diffusion layer HZLc is notdisposed on the bank pattern BNKP disposed at a boundary of each pixelPXLc, the light emitted from the light emitting element LD may beprevented or substantially prevented from being diffused and emitted toan adjacent pixel through the light diffusion layer HZLc. Therefore, thecolor mixture between adjacent pixels may be prevented or substantiallyprevented.

Herein, a pixel unit consisting of a plurality of pixels will bedescribed. The pixel unit may include a light conversion layer thatconverts light emitted from the light emitting element. The structure ofeach pixel included in the pixel unit may be similar to or the same asthat described above, and the same components are denoted by the samereference numerals, and the description thereof may be omitted orsimplified.

FIG. 13 is a top plan view of a pixel unit according to an embodiment;and FIG. 14 is a cross-sectional view taken along the line III-III′ ofFIG. 13. FIG. 15 is a cross-sectional view showing an embodiment inwhich a light diffusion layer of FIG. 14 is disposed on a lightconversion layer, taken along a line corresponding to the line III-III′of FIG. 13. FIG. 16 is a cross-sectional view showing an embodiment inwhich a light diffusion layer of FIG. 14 is not disposed and a lightconversion layer includes a light diffusion particle, taken along a linecorresponding to the line III-III′ of FIG. 13.

Referring to FIGS. 13 and 14, the pixel unit PXU may include a firstpixel PXL1, a second pixel PXL2, and a third pixel PXL3 arrangedsequentially.

As described above, the first pixel PXL1 may emit light of the firstcolor, the second pixel PXL2 may emit light of the second color, and thethird pixel PXL3 may emit light of the third color. The bank patternBNKP may be disposed at the boundaries of the first to third pixelsPXL1, PXL2, and PXL3, and the first to third pixels PXL1, PXL2, and PXL3may be separated from each other by the bank pattern BNKP.

The pixel unit PXU may include a light conversion layer LCL disposed oneach light emitting element LD. In an embodiment, the light conversionlayer LCL may be disposed on the light diffusion layer HZL.

The light conversion layer LCL may include a first wavelength conversionlayer WCL1, a second wavelength conversion layer WCL2, and a lightscattering layer LSL. The first pixel PXL1 may include the firstwavelength conversion layer WCL1, the second pixel PXL2 may include thesecond wavelength conversion layer WCL2, and the third pixel PXL3 mayinclude the light scattering layer LSL.

Each of the first wavelength conversion layer WCL1, the secondwavelength conversion layer WCL2, and the light scattering layer LSL mayinclude a base resin BR and various particles dispersed inside the baseresin BR.

In an embodiment, the first wavelength conversion layer WCL1 may includea first wavelength conversion particle WC1 dispersed inside the baseresin BR, the second wavelength conversion layer WCL2 may include asecond wavelength conversion particle WC2 dispersed inside the baseresin BR, and the light scattering layer LSL may include a lightscattering particle SC dispersed inside the base resin BR. In anembodiment, the first wavelength conversion layer WCL1 and the secondwavelength conversion layer WCL2 may further include the lightscattering particle SC dispersed inside the base resin BR.

The base resin BR is not particularly limited as long as it is amaterial having a high light transmittance and an excellent dispersioncharacteristic for the first wavelength conversion particle WC1, thesecond wavelength conversion particle WC2, and the light scatteringparticle SC. For example, the base resin BR may include an organicmaterial, such as an epoxy resin, an acrylic resin, a cardo resin, animide resin, and the like.

The first wavelength conversion particle WC1 of the first wavelengthconversion layer WCL1 and the second wavelength conversion particle WC2of the second wavelength conversion layer WCL2 may convert a peakwavelength of incident light into another specific peak wavelength. Thatis, the first wavelength conversion particle WC1 and the secondwavelength conversion particle WC2 may convert a color of the incidentlight.

For example, the light emitting element LD may emit blue light, and thefirst wavelength conversion particle WC1 may convert blue light providedfrom the light emitting element LD into red light and may emit the redlight. In addition, the second wavelength conversion particle WC2 mayconvert blue light provided from the light emitting element LD intogreen light and emit the green light. That is, the first pixel PXL1 inwhich the first wavelength conversion layer WCL1 is disposed may be aregion emitting red light, and the second pixel PXL2 in which the secondwavelength conversion layer WCL2 is disposed may be a region emittinggreen light.

For example, the first wavelength conversion particle WC1 and the secondwavelength conversion particle WC2 may include a quantum dot, a quantumrod, phosphor, or the like. The quantum dot may be a particulatematerial that emits light of a certain wavelength while electrontransits from a conduction band to a valence band.

In an embodiment, the quantum dot may be a semiconductor nano-crystalmaterial. The quantum dot may have a specific band gap depending on thecomposition and size thereof to absorb light, and then may emit lighthaving a unique wavelength. Examples of the semiconductor nano-crystalof the quantum dot may include a Group IV nano-crystal, a Group II-VIcompound nano-crystal, a Group III-V compound nano-crystal, and a GroupIV-VI nano-crystal or a combination thereof.

For example, the Group IV nano-crystal may include a binary compound,such as silicon (Si), germanium (Ge), silicon carbide (SiC),silicon-germanium (SiGe), and the like, but the present invention is notlimited thereto.

In addition, the Group II-VI compound nano-crystal may include a binarycompound, such as CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe,MgSe, MgS, and a mixture thereof, a tertiary compound, such as CdSeS,CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS,CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe,MgZnS, and a mixture thereof, or a quaternary compound, such as HgZnTeS,CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS,HgZnSeTe, HgZnSTe, and a mixture thereof, but the present invention isnot limited thereto.

In addition, the Group III-V compound nano-crystal may include a binarycompound, such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP,InAs, InSb, and a mixture thereof, a tertiary compound, such as GaNP,GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP,InNP, InNAs, InNSb, InPAs, InPSb, and a mixture thereof, or a quaternarycompound, such as GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP,GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs,InAlPSb, and a mixture thereof, but the present invention is not limitedthereto.

The Group IV-VI nano-crystals may include a binary compound, such asSnS, SnSe, SnTe, PbS, PbSe, PbSe, PbTe, and a mixture thereof, atertiary compound, such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe,SnPbS, SnPbSe, SnPbTe, and a mixture thereof, or a quaternary compound,such as SnPbSSe, SnPbSeTe, SnPbSTe, and a mixture thereof, but thepresent invention is not limited thereto.

A shape of the quantum dot is a shape generally used in the art and isnot particularly limited, and may be, for example, any of spherical,pyramidal, multi-arm-shaped or cubic nanoparticles, nanotubes,nanowires, nanofibers, and nanoplate-shaped particles, and the like. Thebinary compound, the tertiary compound, or the quaternary compounddescribed above may exist in the same particle with a uniformconcentration, or may exist in the same particle divided into states inwhich concentration distributions are partially different.

In an embodiment, the quantum dot may have a core-shell structureincluding a core including the nano-crystal described above and a shellsurrounding the core. An interface between the core and the shell mayhave a concentration gradient that a concentration of an elementexisting in the shell decreases toward the center thereof. The shell ofthe quantum dot may serve as a protective layer for preventing achemical denaturation of the core to maintain a semiconductorcharacteristic and/or a charging layer for providing a electrophoreticcharacteristic to the quantum dot. The shell may be a single layer ormultiple layers. Examples of a shell of a quantum dot may be oxide of ametal or a nonmetal, a semiconductor compound, or a combination thereof.

For example, the oxide of a metal or a nonmetal may be a binarycompound, such as SiO₂, Al₂O₃, TiO₂, ZnO, MnO, Mn₂O₃, Mn₃O₄, CuO, FeO,Fe₂O₃, Fe₃O₄, CoO, Co₃O₄, NiO, or a quaternary compound, such asMgAl₂O₄, CoFe₂O₄, NiFe₂O₄, CoMn₂O₄, and the like, but the presentinvention is not limited thereto.

In addition, the semiconductor compound may be any of CdS, CdSe, CdTe,ZnS, ZnSe, ZnTe, ZnSeS, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP,InSb, AlAs, AlP, AlSb, and the like, but the present invention is notlimited thereto.

In an embodiment, the light emitted by the quantum dot may have a fullwidth of half maximum (FWHM) of about 45 nm or less, thereby improving acolor purity and a color reproducibility of a color displayed by thedisplay device. In addition, the light emitted by the quantum dot may beemitted in various directions regardless of an incident direction of theincident light. Therefore, a lateral visibility of the display devicemay be improved.

In an embodiment, both the first wavelength conversion particle WC1 andthe second wavelength conversion particle WC2 may consist of the quantumdot. In an embodiment, a diameter of the quantum dot constituting thefirst wavelength conversion particle WC1 may be greater than a diameterof the quantum dot constituting the second wavelength conversionparticle WC2. For example, the diameter of the quantum dot constitutingthe first wavelength conversion particle WC1 may be about 55 Å to 65 Å,and the diameter of the quantum dot constituting the second wavelengthconversion particle WC2 may be about 40 Å to 55 Å, but the presentinvention is not limited thereto.

The light scattering layer LSL may include a light scattering particleSC. In addition, as described above, the first wavelength conversionlayer WCL1 and the second wavelength conversion layer WCL2 may furtherinclude a light scattering particle SC.

The light scattering particle SC may form an optical interface with thebase resin BR with a different refractive index than the base resin BR.The light scattering particle SC is not particularly limited as long asit is a material capable of scattering at least some of transmittedlight. For example, the light scattering particle SC may be an oxideparticle, such as any of titanium oxide (TiO₂), aluminum oxide (Al₂O₃),indium oxide (In₂O₃), zinc oxide (ZnO), tin oxide (SnO₂), and silica.

The light scattering particle SC may scatter light in a random directionregardless of an incident direction of an incident light, withoutsubstantially changing a wavelength of light transmitting through thelight scattering layer LSL. Therefore, a lateral visibility of thedisplay device may be improved.

In an embodiment, a passivation layer PSV may be disposed on the lightconversion layer LCL. The passivation layer PSV may include an inorganicinsulating layer consisting of an inorganic material, may preventmoisture and/or oxygen from penetrating into the light conversion layerLCL from the outside, and may protect the wavelength conversionparticles WC1 and WC2.

As described above, the light conversion layer LCL may be disposed onthe light diffusion layer HZL. The light emitted from the light emittingelement LD may be diffused by the light diffusion layer HZL to beuniformly incident on the light conversion layer LCL. Accordingly, aconversion efficiency of light incident into the light conversion layerLCL may be improved, and uniform light as a whole in a plane view may beemitted to the outside. Particularly, since the light incident on thefirst wavelength conversion layer WCL1 and the second wavelengthconversion layer WCL2 is converted into a uniform color as a whole, itis possible to prevent or substantially prevent a color of the emittedlight from varying in each region.

FIG. 15 and FIG. 16 are cross-sectional views of a pixel unit accordingto further embodiments. Herein, a difference from the embodiment shownin FIG. 14 will be described mainly.

FIG. 15 shows an embodiment in which a light diffusion layer of FIG. 14is disposed on a light conversion layer and is a cross-sectional viewtaken along a line corresponding to the line III-III′ of FIG. 13.

Referring to FIG. 15, a pixel unit PXUd may include first to thirdpixels PXL1 d, PXL2 d, and PXL3 d, and the first to third pixels PXL1 d,PXL2 d, and PXL3 d may include a light diffusion layer HZL disposed on alight conversion layer LCL.

In an embodiment, the light diffusion layer HZL may be directly disposedon a passivation layer PSV covering the light conversion layer LCL. Inan embodiment, the light diffusion layer HZL may be entirely disposed onthe passivation layer PSV. However, the present invention is not limitedthereto, and the light diffusion layer HZL may be patterned and disposedonly in some regions, as in the embodiment shown in FIG. 12. In anotherembodiment, the light diffusion layer HZL may be directly disposed onthe light conversion layer LCL. In an embodiment, the light diffusionlayer HZL may be disposed between the light conversion layer LCL and thepassivation layer PSV.

The light diffusion layer HZL may uniformly diffuse light emitted fromthe light conversion layer LCL. Accordingly, a uniformity of the lightemitted from the display device may be improved.

FIG. 16 shows an embodiment in which the light diffusion layer of FIG.14 is not disposed and the light conversion layer includes a lightdiffusion particle, and is a cross-sectional view taken along a linecorresponding to the line III-III′ of FIG. 13.

Referring to FIG. 16, a pixel unit PXUe may include first to thirdpixels PXL1 e, PXL2 e, and PXL3 e, and the first to third pixels PXL1 e,PXL2 e, and PXL3 e may include a first wavelength conversion layer WCL1e, a second wavelength conversion layer WCL2 e, and a light scatteringlayer LSLe.

The first wavelength conversion layer WCL1 e, the second wavelengthconversion layer WCL2 e, and the light scattering layer LSLe may serveas a light diffusion layer including the light diffusion particle HZP.

The first wavelength conversion layer WCL1 e, the second wavelengthconversion layer WCL2 e, and the light scattering layer LSLe may furtherinclude a light diffusion particle HZP dispersed in the base resin BR.

For example, the light diffusion particle HZP may include silvernanowires (AgNW), but is not limited thereto.

Light emitted from the light emitting element LD may be diffused by thelight diffusion particle HZP inside the light conversion layer LCLe.Accordingly, uniform light as a whole may be emitted from each of thepixels PXL1 e, PXL2 e, and PXL3 e.

In addition, when the light conversion layer LCLe includes the lightdiffusion particle HZP, it is possible to shorten a curing time of thebase resin BR in which various particles are dispersed in amanufacturing process of the light conversion layer LCLe. That is, amanufacturing cost of the display device may be reduced.

While some example embodiments of the invention are described withreference to the attached drawings, it will be understood by those ofordinary skill in the technical field to which the present inventionpertains that the present invention may be carried out in other formswithout departing from the spirit and scope of the present invention.Accordingly, the above-described example embodiments should beconsidered in a descriptive sense only and not for purposes oflimitation.

What is claimed is:
 1. A display device comprising: a substrate; a firstelectrode and a second electrode arranged to be spaced apart from eachother on the substrate; a first insulating layer on the substrate; alight emitting element on the first insulating layer, located betweenthe first electrode and the second electrode, and comprising a first endportion and a second end portion; a third electrode on the substrate andelectrically connected to the first electrode and the first end portion;a fourth electrode on the substrate and electrically connected to thesecond electrode and the second end portion; a second insulating layeron the substrate and covering the light emitting element, the thirdelectrode, and the fourth electrode; and a light diffusion layer on thesecond insulating layer and comprising a light diffusion particle. 2.The display device of claim 1, wherein the light diffusion particlecomprises at least one of a silver nanowire, a gold nanowire, a carbonnanowire, and a nickel nanowire.
 3. The display device of claim 2,wherein the light diffusion layer further comprises a light scatteringparticle, and the light scattering particle comprises at least one oftitanium oxide (TiO₂), aluminum oxide (Al₂O₃), indium oxide (In₂O₃),zinc oxide (ZnO), tin oxide (SnO₂), and silica.
 4. The display device ofclaim 1, further comprising a first bank and a second bank on thesubstrate and arranged to be spaced apart from each other, wherein thefirst bank overlaps with the first electrode, and the second bankoverlaps with the second electrode.
 5. The display device of claim 4,wherein the first insulating layer comprises a first opening exposing atleast a portion of the first electrode, and a second opening exposing atleast a portion of the second electrode, and the first opening overlapswith the first bank, and the second opening overlaps with the secondbank.
 6. The display device of claim 1, wherein a space is definedbetween the light emitting element and the first insulating layer. 7.The display device of claim 1, further comprising a first insulatingpattern on the light emitting element, wherein the first insulatingpattern exposes the first end portion and the second end portion of thelight emitting element.
 8. The display device of claim 1, furthercomprising a second insulating pattern on the third electrode, whereinthe second insulating pattern is arranged both on a region comprisingthe first end portion of the light emitting element and on the thirdelectrode, and covers an end of the third electrode on the lightemitting element.
 9. The display device of claim 1, further comprising abank pattern on the substrate and surrounding the light emitting elementin a plane view.
 10. The display device of claim 9, wherein the lightdiffusion layer overlaps with the light emitting element and does notoverlap with the bank pattern.
 11. The display device of claim 1,further comprising a wavelength conversion layer on the light emittingelement and comprising a wavelength conversion particle, wherein thewavelength conversion particle comprises a quantum dot.
 12. A displaydevice comprising: a first pixel in a display area, wherein the firstpixel comprises: a substrate; a first electrode and a second electrodearranged to be spaced apart from each other on the substrate; a firstinsulating layer on the substrate and exposing a portion of the firstelectrode and a portion of the second electrode; a light emittingelement on the first insulating layer, located between the firstelectrode and the second electrode, and comprising a first end portionand a second end portion; a third electrode on the substrate andelectrically connected to the first electrode and the first end portion;a fourth electrode on the substrate and electrically connected to thesecond electrode and the second end portion; a second insulating layeron the substrate and covering the light emitting element, the thirdelectrode, and the fourth electrode; a light diffusion layer on thesecond insulating layer and comprising a light diffusion particle; and afirst wavelength conversion layer on the substrate and comprising afirst wavelength conversion particle, wherein the light emitting elementemits light of a first color, and the first wavelength conversionparticle converts the light of the first color into light of a secondcolor.
 13. The display device of claim 12, wherein the light diffusionparticle comprises at least one of a silver nanowire, a gold nanowire, acarbon nanowire, and a nickel nanowire.
 14. The display device of claim13, further comprising a second pixel in the display area and arrangedadjacent to the first pixel, wherein the second pixel comprises a secondwavelength conversion layer comprising a second wavelength conversionparticle, and the second wavelength conversion particle converts thelight of the first color into light of a third color.
 15. The displaydevice of claim 14, further comprising a third pixel in the display areaand arranged adjacent to the first pixel and the second pixel, whereinthe third pixel comprises a light scattering particle, and the lightscattering particle comprises at least one of titanium oxide (TiO₂),aluminum oxide (Al₂O₃), indium oxide (In₂O₃), zinc oxide (ZnO), tinoxide (SnO₂), and silica.
 16. The display device of claim 14, furthercomprising a bank pattern between the first pixel and the second pixel,wherein the light diffusion layer does not overlap with the bankpattern.
 17. The display device of claim 12, wherein the light diffusionlayer is between the light emitting element and the first wavelengthconversion layer.
 18. The display device of claim 12, further comprisinga passivation layer covering the first wavelength conversion layer,wherein the light diffusion layer is on the passivation layer.
 19. Adisplay device comprising: a substrate; a first electrode and a secondelectrode arranged to be spaced apart from each other on the substrate;a first insulating layer on the substrate; a light emitting element onthe first insulating layer, located between the first electrode and thesecond electrode, and comprising a first end portion and a second endportion; a third electrode on the substrate and electrically connectedto the first electrode and the first end portion; a fourth electrode onthe substrate and electrically connected to the second electrode and thesecond end portion; a second insulating layer on the substrate andcovering the light emitting element, the third electrode, and the fourthelectrode; and a wavelength conversion layer provided on the secondinsulating layer and comprising a wavelength conversion particle and alight diffusion particle, wherein the light diffusion particle comprisesat least one of a silver nanowire, a gold nanowire, a carbon nanowire,and a nickel nanowire.